Method for generating thermal energy from fine-grained oilseeds, preferably from rapeseed, and device for carrying out the method

ABSTRACT

The invention relates to an arrangement for utilizing small-grained oilseeds, preferably rapeseed, without the need for prior processing of the seeds such as expressing the oil, in which a pressure of at least 2 bar is maintained in the combustion space ( 2 ) of a combustion chamber ( 1 ). In this combustion space, an oil or gas burner ( 8 ) is provided, which preheats the combustion space ( 2 ) to a temperature of at least c. 1000° C., causing the initial seeds fed into the combustion space ( 2 ) through a feed line ( 3 ) to ignite, if the required combustion air is supplied at the same time through a combustion air supply line ( 6 ). The seeds fed in subsequently through the feed line bum explosively in a chain reaction if the combustion air is supplied in controlled amounts, and if the required pressure is maintained in the combustion space. The resulting flame exits through a flame exit opening ( 9 ) and can be used for heating purposes.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing thermal energy fromsmall-grained oilseeds, preferably from rapeseed. The invention alsorelates to an arrangement for the implementation of such a method.

It is already known from prior art that rapeseed oil produced bypressing the seeds can be burned and that the resulting thermal energycan be utilized. However, such a production of rapeseed oil requires aseparate operation, which means that such a method is cost-intensive.Furthermore, the hulls of the seeds, which remain after pressing, mustbe removed separately, for example by incinerating them in specialburners.

An arrangement for producing thermal energy is known from U.S. Pat. No.5,249,952, which shows combustion air supply lines which lead intoseveral combustion chambers arranged in succession. One of thesecombustion chambers has a feed line for liquid and/or gaseouscombustible substances and a feed line for solids, which can be admixedduring the combustion process in this combustion chamber. To start thecombustion process, it is provided with a sparkplug which can ignite anoil that is being supplied. With this known arrangement, it is notpossible to bum the unreduced seeds of oil crops without an additionalsupply of liquid and/or gaseous fuels.

SUMMARY OF THE INVENTION

It is an object of the present invention to avoid the above-mentioneddisadvantages and to create a method and an arrangement for producingthermal energy from small-grained oilseeds, preferably from rapeseed,with which the seeds can be burned without the need of prior processing.To achieve this objective, the invention proposes a method in which thecombustion space of a combustion chamber is first preheated, and inwhich unreduced seeds and combustion air are supplied in controlledamounts, after which the preheating ends and a pressure of at least 2bar is maintained in the combustion space, whereby the subsequentlysupplied oilseeds burn explosively, and the resulting flame exitsthrough a flame exit opening.

It has been found that after the seeds fed in first have ignited due tothe temperature in the preheated combustion space, the seeds fed insubsequently are burning explosively in a chain reaction if thecombustion air is delivered in controlled amounts as needed, and if therequired pressure is maintained in the combustion space. It is notnecessary to process the seeds before they are fed into the combustionspace, which means a considerable simplification of the method and areduction in cost. It is sufficient only to ensure a continuouslycontrolled supply of seeds into the combustion space, preferablyindividually in succession.

Preferably, the combustion space of a combustion chamber is preheated toa temperature between 500° C. and 1250° C., for example, to atemperature of c. 1000° C. This temperature ensures the ignition of theseeds fed into the combustion space first, and the preheating processcan be ended after such ignition.

An uninterrupted chain reaction during the explosive combustion of theseeds is ensured if a pressure between 2 bar and 13 bar is maintained inthe combustion chamber; the maximum values of pressure represent peakvalues which occur during the explosion of the seeds.

Preferably, the seeds of the oil crops fed in are forced to perform aspiral movement in at least one section of the combustion space, whichprolongs their retention time in the combustion space and thus ensuresthe complete combustion of all the seeds fed in.

It is furthermore an advantage if the volume of the combustion space isvariable, so that the pressure existing in the combustion space can becontrolled as well and can be adapted to the requirements, especially inthe starting phase during the preheating process.

An arrangement for implementing the method according to the invention ischaracterized substantially by a combustion chamber with a combustionspace in which a disconnectible preheating device, such as an oilburner, is provided, leading into which are a feed line for feeding inthe oilseeds and at least one combustion air supply line, and which isprovided with a flame exit opening, whereby devices for maintaining apressure in the combustion space are provided. In such an arrangement,the seeds are fed in controlled amounts through the feed line into thecombustion space, where they are explosively burned after initialignition due to the temperature following preheating, while the requiredamount of combustion air is present and while the required pressure ismaintained, whereby the resulting flame exits from the flame exitopening and delivers its heat energy.

If the oilseeds are fed in through the feed line and the requiredcombustion air is delivered through the combustion air supply line withpositive pressure, a pressure drop can be prevented in the combustionspace. However, to ensure that the arrangement according to theinvention operates satisfactorily, it is advantageous when, according toa further embodiment of the invention, the required pressure in thecombustion space is maintained by means of pressure control devicesprovided in the feed line for feeding in the seeds and/or in the area ofthe flame exit opening.

It is practical when a controllable proportioning device is provided inthe feed line for feeding in the oilseeds, which not only adapts theamount of fed-in seeds to the combustion process, but can also bedesigned as a pressure control device.

In a preferred embodiment of the arrangement according to the invention,the combustion space consists of an interior tube and an exterior casingwhich surrounds the interior tube with clearance and communicates withthe interior tube. This results in a design which, in spite of itscompact size, ensures the required retention time of the oilseeds in thecombustion space.

In such an embodiment, it is an advantage if the feed line for feedingin the seeds leads into the interior tube in which the disconnectiblepreheating device is arranged, and if the flame exit opening is providedin the exterior casing. In that case, the oilseeds are first fed throughthe feed line into the interior tube, which was heated by the preheatingdevice to a temperature at which the initial ignition takes place.Subsequently, the preheating device can be disconnected, since thetemperature required for igniting the individual seeds is maintained bythe combustion process. The oilseeds fed into the interior tube passthrough the interior tube into the exterior casing, which communicateswith the interior tube, where afterburning occurs until finally theresulting flame exits through the flame exit opening. Due to the factthat the feed line leads into the interior tube and thus penetrates thespace defined by the exterior casing where afterburning occurs, theseeds are already heated in the section of the feed line whichpenetrates the space before the seeds enter the interior tube, thuspromoting the combustion process in the interior tube.

It has been found advantageous to provide the interior wall of theinterior tube with a spiral recess, whereby the feed line preferentiallyleads tangentially into the interior tube. This design forces theoilseeds fed into the interior tube to perform a spiral movement, thusenlarging the path of the seeds inside the interior tube and prolongingtheir retention time in the interior tube.

As already mentioned, it is advantageous if the volume of the combustionspace is variable. For that purpose, according to the invention, a wallof the exterior casing, preferably an end wall that extendsperpendicular to the axis of the interior tube, can be of adjustabledesign. By adjusting the wall, the volume of the combustion space isenlarged when the arrangement according to the invention is started, andthe pressure control devices in the area of the flame exit opening alsoare adjusted in such a way that the low pressure required in thecombustion space during the starting process is ensured. After initialignition has occurred, the volume of the combustion space is decreased,thus ensuring the pressure required for the explosive combustion of theoilseeds.

It is practical to design one wall of the exterior casing as a platethat is movable, preferably by means of an electrical actuator.According to the invention, at least one combustion air supply lineleads into the interior tube, preferably tangentially, ensuring that theamount of combustion air required for the combustion of the oilseeds isavailable there. The tangential delivery of the combustion air promotesthe spiral movement of the seeds in the interior tube.

To ensure complete afterburning in the space enclosed by the exteriorcasing, another combustion air supply line for delivering secondary aircan lead into this space.

It is practical to provide a controllable blower in at least onecombustion air supply line, which controls the amount of combustion airneeded for the explosive combustion. This blower can be designed in sucha way that it serves as a pressure controller device for maintaining therequired pressure in the combustion space.

To provide pressure control in the area of the flame exit opening, theflame exit opening may, for example, be designed as a Venturi nozzle,whereby it is advantageous to design the flame exit opening as amulti-stage Venturi nozzle. In that case, an afterburner device can beprovided between the individual stages, where the afterburning of theunburned gases can take place. Preferably, however, in the flame exitopening, which is preferably designed as a pipe end, at least onethrottle is provided with which the pressure in the combustion space canbe controlled by changing the flap position.

To maintain the pressure in the combustion space, the flame exit openingmay also be designed as a labyrinth.

As already mentioned, considerably high temperatures occur in thecombustion space. To prevent damage caused by these temperatures, it isadvantageous to construct the combustion chamber with the combustionspace, in particular the interior tube and the surrounding exteriorcasing, from a fire resistant, preferably ceramic, material. However,the combustion space may also be surrounded by a cooling jacket, whichprevents overheating.

The arrangement according to the invention is described by means ofexamples of embodiments shown in schematic view in the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section of a first embodiment of the arrangementaccording to the invention; and

FIG. 2 shows another embodiment of the arrangement according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The arrangement shown in FIG. 1 consists of a combustion chamber 1 witha combustion space 2. Leading into this combustion space 2 is a feedline 3 through which small-grained oilseeds are fed individually insuccession from a reservoir 4 into the combustion space 2 through acontrollable proportioning device 5, and a combustion air supply line 6with a controllable blower 7. It must be ensured that after initialignition has occurred, the pressure does not drop in combustion space 2either through feed line 3 or through combustion air supply line 6. Forthat purpose, lines 3 and 6 may be provided with separate devices formaintaining the pressure in combustion space 2. However, it isadvantageous to design the controllable proportioning device 5 and thecontrollable blower 7 in such a way that these devices also ensure thatpressure is maintained in combustion space 2.

Combustion space 2 also contains a disconnectible preheating device 8 inthe form of an oil burner.

When the arrangement according to the invention is started up,combustion space 2 is first of all preheated to a temperature of c.1000° C. by means of the preheating device 8, after which apredetermined amount of seeds is fed to combustion space 2 through feedline 3, and these seeds ignite due to the high temperature in combustionspace 2. Subsequently, additional individual seeds, whose number can becontrolled by proportioning device 5, are fed in. At the same time, anamount of combustion air required for the complete combustion of theseeds is delivered through combustion air supply line 6 and thecontrollable blower 7. The unreduced seeds fed in succession are ignitedexplosively by the already burning seeds, resulting in a chain reactionwhich ensures the complete combustion without residue, after which thepreheating device 8 can be disconnected.

The resulting flame exits from flame exit opening 9 and can then beutilized for heating purposes. Here, too, it must be ensured that nopressure drop results in the combustion space through this flame exitopening 9. In the embodiment shown as an example, this is accomplishedbecause the flame exit opening is designed as a Venturi nozzle. Thedrawing shows only a one-stage Venturi nozzle, but in some cases itwould be an advantage to provide a multi-stage Venturi nozzle withafterburner devices between the individual stages, which is not onlycertain to prevent a pressure drop in combustion space 2, but alsoensures that the energy inherent in the oilseeds is completely utilized.

Instead of designing the flame exit opening as a Venturi nozzle, it canalso be designed as a labyrinth.

The overheating of combustion chamber 1 is prevented by surroundingcombustion space 2 with a cooling jacket 10.

In the embodiment of the arrangement according to the invention shown inFIG. 2, combustion space 2 consists of an interior tube 11 and anexterior casing 12 which surrounds the interior tube 11 with clearanceand is also designed as a tube that extends coaxially to interior tube11. A feed line 3, through which the small-grained oilseeds are fed froma storage container (not shown) to interior tube 1, leads tangentiallyinto the interior tube. It is practical if the air that is used as theconveyance medium also forms part of the combustion air.

Also leading tangentially into interior tube 11 is a combustion airsupply line 6 through which the primary air needed for the combustion ofthe seeds in the interior tube is delivered. The interior wall ofinterior tube I 1 is provided with a spiral recess 13 which forces thefed-in seeds to perform a spiral movement, thus prolonging theirretention time in the interior tube.

One end of the interior tube is closed by a wall 14, in which a pipe end15 is provided into which a preheating device 8 extends which may, forexample, consist of a gas burner. The opposite end of interior tube 11is open, allowing the interior tube to communicate with space 16surrounded by exterior casing 12. Leading into this space 16 is pipe end17 which forms flame exit opening 9 and which is provided with throttles18. Furthermore, in the area of the open end of interior tube 12, space16 is connected to another air supply line 19 which delivers secondaryair.

One wall of exterior casing 12 is formed as a movable plate 20. It ismoved via a rod 21 by means of an electrical actuator (not shown). Bychanging the position of plate 20, the volume of space 16 and thus ofthe combustion chamber can be varied.

Interior tube 11 and exterior casing 12 as well as plate 20 consist offire resistant, in particular ceramic, material that is able towithstand temperatures up to 1600° C. which occur during the combustionof the seeds.

When the arrangement according to the invention, shown in FIG. 2, isstarted up, interior tube 11 is first of all preheated with preheatingdevice 8 to a temperature required for the combustion of the seeds, forexample to a temperature of 1000° C. Subsequently, a certain quantity ofseeds is fed into the interior tube through feed line 3. The seeds movealong spiral recess 13 and are ignited by the hot wall of the interiortube. During this, plate 20 is in a position in which the volume ofspace 16 is small, and the throttles 18 are open.

After initial ignition of the fed-in seeds has thus occurred, thepreheating device can be disconnected. By changing the position of plate20, the volume of space 16 is enlarged, and the direction of thethrottles 18 is changed to closing position. The seeds successively fedthrough feed line 3 ignite due to the high temperature that now prevailsin interior tube 11, causing a chain reaction, and these seeds burnexplosively if the primary air is appropriately supplied throughcombustion air supply line 11. This prevents the temperature fromdropping. The hot gases which occur at the open end of interior tube 11are reversed and led through space 16 (which is surrounded by exteriorcasing 12 and in which, thanks to the supply of secondary air throughair supply line 19, afterburning takes place) into pipe end 17, wherebythe resulting flame exits from the flame exit opening 9. Byappropriately controlling throttles 18, the required pressure ismaintained in the combustion space. Due to the fact that a section ofoilseed feed line 3 and a section of combustion air supply line 6 passthrough space 16 in which a high temperature prevails, the seeds as wellas the combustion air are preheated before entering interior tube 11,which means that combustion in interior tube 11 is promoted.

What is claimed is:
 1. Method for producing thermal energy fromsmall-grained oilseeds wherein a combustion space of a combustionchamber is first preheated to a temperature between 500° C. and 1250°C., and unreduced seeds as well as combustion air are fed into thecombustion space in controlled amounts, thereafter preheating isdiscontinued, and a pressure of at least 2 bar is maintained in thecombustion space, whereby subsequently fed in seeds burn explosively,and a resulting flame exits through a flame exit opening.
 2. Methodaccording to claim 1 wherein the temperature in the combustion space isabout 1000° C.
 3. Method according to claim 1 including maintaining apressure between 2 bar and 13 bar in the combustion space.
 4. Methodaccording to claim 1 including feeding the oilseeds individually and insuccession into the combustion chamber.
 5. Method according to claim 1including forcing the oilseeds to perform a spiral movement in at leastone section of the combustion space.
 6. Method according to claim 1including varying a volume of the combustion space.
 7. Arrangement forproducing thermal energy from small-grained oilseeds in a continuousprocess comprising a combustion chamber with a combustion space in whicha disconnectible preheating device is provided, and into which lead afeed line for feeding in the oilseeds and at least one combustion airsupply line, and which is provided with a flame exit opening, anddevices in the feed line, the at least one combustion air supply lineand the flame exit opening for maintaining a pressure of at least 2 barin the combustion space.
 8. Arrangement according to claim 7 including acontrollable proportioning device in the feed line for feeding in theoilseeds.
 9. Arrangement according to claim 7 wherein the combustionspace comprises an interior tube and an exterior casing surrounding saidinterior tube with clearance and communicating with said interior tube.10. Arrangement according to claim 9 wherein the feed line leads intothe interior tube in which the disconnectible preheating device arrangedand the flame exit opening is provided in the exterior casing. 11.Arrangement according to claim 9 wherein the interior tube includes aninterior wall with a spiral recess and wherein the feed line leadstangentially into the interior tube.
 12. Arrangement according to claim9 wherein the exterior casing includes an adjustable end wall extendingacross an axis of the interior tube.
 13. Arrangement according to claim12 wherein a wall of the exterior casing comprises a plate that can bemoved by means of an electrical actuator.
 14. Arrangement according toclaim 7 including at least one combustion air supply line leadingtangentially into the interior tube.
 15. Arrangement according to claim14 including another combustion air supply line for the delivery ofsecondary air leading into a space surrounded by the exterior casing.16. Arrangement according to claim 7 including a controllable blowercoupled to the at least one combustion air supply line.
 17. Arrangementaccording to claim 8 wherein the flame exit opening comprises a Venturinozzle.
 18. Arrangement according to claim 17 wherein the flame exitopening comprises a multi-stage Venturi nozzle and an afterburner deviceprovided between different stages of the Venturi nozzle.
 19. Arrangementaccording to claim 7 including at least one throttle in the flame exitopening configured as a pipe end.
 20. Arrangement according to claim 7wherein the flame exit opening is configured as a labyrinth. 21.Arrangement according to claim 7 wherein the combustion chamber and thecombustion space are defined by an interior tube and an exterior casingsurrounding the tube and made of a fire resistant ceramic material. 22.Arrangement according to claim 7 including a cooling jacket surroundingthe combustion space.
 23. Method for producing thermal energy fromsmall-grained oilseeds wherein a combustion space of a combustionchamber is first preheated and unreduced seeds as well as combustion airare fed into the combustion space in controlled amounts, thereafterpreheating is discontinued and a pressure of at least 2 bar ismaintained in the combustion space, whereby subsequently fed in seedsbum explosively, and a resulting flame exits through a flame exitopening, and wherein in at least one section of the combustion space thefed-in oilseeds are forced to perform a spiral movement.
 24. Method forproducing thermal energy from small-grained oilseeds wherein acombustion space of a combustion chamber is first preheated andunreduced seeds as well as combustion air are fed into the combustionspace in controlled amounts, thereafter preheating is discontinued and apressure of at least 2 bar is maintained in the combustion space,whereby subsequently fed in seeds burn explosively, and a resultingflame exits through a flame exit opening, and wherein a volume of thecombustion space is variable.
 25. Arrangement for producing thermalenergy from small-grained oilseeds comprising a combustion chamber witha combustion space in which a disconnectible preheating device isprovided, and into which lead a feed line for feeding in the oilseedsand at least one combustion air supply line, and which is provided witha flame exit opening, devices for maintaining a pressure in thecombustion space, the combustion space comprising an interior tube, andan exterior casing surrounding the interior tube with clearance andcommunicating with the interior tube.
 26. Arrangement for producingthermal energy from small-grained oilseeds comprising a combustionchamber with a combustion space in which a disconnectible preheatingdevice is provided, and into which lead a feed line for feeding in theoilseeds and at least one combustion air supply line, and which isprovided with a flame exit opening, devices for maintaining a pressurein the combustion space, the combustion space comprising an interiortube and an exterior casing surrounding and communicating with theinterior tube, and at least one combustion air supply line leading intothe interior tube.
 27. Arrangement for producing thermal energy fromsmall-grained oilseeds comprising a combustion chamber with a combustionspace in which a disconnectible preheating device is provided, and intowhich lead a feed line for feeding in the oilseeds and at least onecombustion air supply line, and which is provided with a flame exitopening, devices for maintaining a pressure in the combustion space, andat least one throttle in the flame exit opening which is designed as apipe end.